Frequency-dependent changes in amplitude of low-frequency oscillations in depression: A resting-state fMRI study

•Distant spatial profiles were observed in the low amplitudes of the slow-4 versus slow-5 frequency bands derived from resting-state fMRI signals.•MDD patients showed altered ALFF and fALFF in widely distributed brain regions.•The alteration in ALFF and fALFF in MDD patients were dependent on the choice of different frequency bands. We conducted this fMRI study to examine whether the alterations in amplitudes of low-frequency oscillation (LFO) of major depressive disorder (MDD) patients were frequency dependent. The LFO amplitudes (as indexed by amplitude of low-frequency fluctuation [ALFF] and fractional ALFF [fALFF]) within 4 narrowly-defined frequency bands (slow-5: 0.01–0.027Hz, slow-4: 0.027–0.073Hz, slow-3: 0.073–0.198Hz, and slow-2: 0.198–0.25Hz) were computed using resting-state fMRI data of 35 MDD patients and 32 healthy subjects. Repeated-measures analysis of variance (ANOVA) was performed on ALFF and fALFF both within the low frequency bands of slow-4 and slow-5 and within all of the four bands. We observed significant main effects of group and frequency on ALFF and fALFF in widely distributed brain regions. Importantly, significant group and frequency interaction effects were observed in the ventromedial prefrontal cortex, inferior frontal gyrus, precentral gyrus, in a left-sided fashion, the bilateral posterior cingulate and precuneus, during ANOVA both within slow-4 and slow-5 bands and within all the frequency bands. The results suggest that the alterations of LFO amplitudes in specific brain regions in MDD patients could be more sensitively detected in the slow-5 rather than the slow-4 bands. The findings may provide guidance for the frequency choice of future resting-state fMRI studies of MDD.